A typical LCD has the advantages of portability, low power consumption, and low radiation. LCDs have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
The LCD usually includes a color filter (CF) substrate, a thin film transistor (TFT) array substrate, and a liquid crystal layer sandwiched between the two substrates. When the LCD works, an electric field is applied to the liquid crystal molecules of the liquid crystal layer. At least some of the liquid crystal molecules change their orientations, whereby the liquid crystal layer provides anisotropic transmittance of light therethrough. Thus the amount of the light penetrating the CF substrate is adjusted by controlling the strength of the electric field. In this way, desired pixel colors are obtained at the CF substrate, and the arrayed combination of the pixel colors provides an image viewed on a display screen of the LCD.
If an electric field continues to be applied to the liquid crystal material in one direction, the liquid crystal material may deteriorate. Therefore, in order to avoid this problem, gradation voltages that are provided to pixel electrodes of the TFT array substrate are switched from a positive value to a negative value with respect to a common voltage. This technique is referred to as an inversion drive method. Normally, the inversion drive method includes a frame inversion, a row inversion, and a column inversion. Because the inversion drive method needs the common voltage to be a predetermined constant value in order to avoid flickers on the screen of the LCD, common voltage parameters are written in a driving integrated circuit of the LCD during manufacturing of the LCD.
Referring to FIG. 5, a typical method of manufacturing an LCD includes the following steps.
In step S110, an LCD panel is manufactured. This step includes providing a thin film transistor substrate and a color filter substrate, combining the thin film transistor substrate with the color filter substrate to form a space therebetween, and filling liquid crystal molecules in the space defined by the two substrates.
In step S120, the LCD panel is tested. This step includes lighting up the LCD panel, and inputting a plurality of test image signals with different gray-scales to the LCD panel for testing the quality of the corresponding images displayed by the LCD panel. The testing is intended to detect whether there are any abnormalities such as line defects or dot defects.
In step S130, at least one driving integrated circuit and a flexible printed circuit board are mounted on the LCD panel. This step includes cutting off a plurality of test lines on the LCD panel used for testing the LCD panel in step S120, and fixing the driving integrated circuit and the flexible printed circuit board on the LCD panel.
In step S140, the LCD panel having the driving integrated circuit and the flexible printed circuit board is inspected to confirm that no breaks or defects exist on the LCD panel after the execution of step S130.
In step S150, a preferred common voltage of the LCD panel is obtained. This step includes detecting the degree of the flicker of the LCD panel, adjusting the common voltage of the LCD panel according to the degree of the flicker in order to depress or eliminate the flicker of the LCD panel, and recording parameters of the preferred common voltage when the flicker of the LCD panel is lowest or absent altogether.
In step S160, the parameters of the preferred common voltage are written into the driving integrated circuit.
Referring to FIG. 6, in step S160, an OTP programmer 100 is used to write the parameters of the preferred common voltage into the driving integrated circuit 102 of the LCD panel 101. The driving integrated circuit 102 includes a common voltage adjusting circuit (not shown), and a one time programmable (OTP) read-only memory (ROM). The OTP programmer 100 includes an image generator 104, a writing voltage generator 105, and a processing controller 106. The image generator 104, the writing voltage generator 105, and the processing controller 106 are electrically connected to the driving integrated circuit 102 via a flexible printed circuit board 103. The image generator 104 is configured to generate flicker test images, and provide the flicker test images to the driving integrated circuit 102 for testing the LCD panel 101. The common voltage adjusting circuit of the driving integrated circuit 102 is configured to confirm the preferred common voltage of the LCD panel 101 as described in step S150, and transmit the parameters of the preferred common voltage to the writing voltage generator 105. The writing voltage generator 105 generates a plurality of voltages according to the parameters of the preferred common voltage. The processing controller 106 is configured to write the voltages representing the parameters of the preferred common voltage to the OTP ROM of the driving integrated circuit 102.
Because the preferred common voltage is confirmed by the driving integrated circuit 102, the method for manufacturing the LCD panel 101 needs the two steps S120 and S150: to light up the LCD panel 101 for testing the quality of the LCD panel 101, and confirm the preferred common voltage, respectively. Every step required adds to the complexity and cost of manufacturing the LCD panel 101. Thus the method for manufacturing the LCD is correspondingly complex and costly.
It is desired to provide a method for manufacturing an LCD panel which can overcome the above-described deficiencies.